The toe: effects on corner handling, straight-line speed and tire wear

THE TOE

TKART Staff

22 January 2016

Toe is a fundamental parameter of kart performance that affects how corner entry handling, straight-line speed and tire wear

WHAT IS IT?

HOW DOES IT WORK?

IN PRACTICE

The toe is the angle formed between front wheels and the kart’s longitudinal axis. This angle is responsible for how fast the kart goes on straights, how it handles corner entry, and how tires wear.
Taking the distance between the front tires and that between the rear tires, toe angle can be calculated based on this formula:
TgA = (Lf – Lr)/2/ D
A = arctg ((Lf – Lr)/2/D)

TgA is the tangent of the toe angle; Lf and Lr are front and rear distance

between tires; D is tire wheel diameter.
Math aside, measuring toe by using alignment discs on the front hubs instead yields more precise and effective results.
Toe-out (positive toe angle) is when front tires are farther apart compared to rear tires, i.e. they are angled outwards. Vice versa, toe-in (negative toe) is when they are closer together than rear tires, i.e. they are angled inwards. Zero toe is when Lf = Lr, i.e. front tires are perfectlty parallel to the kart, just like rear tires.

THE STRUCTURAL ELEMENTS RESPONSIBLE FOR TOE ARE THE STEERING RODS, WHICH CONNECT THE STUB AXLES TO THE STEERING COLUMN

WHAT IS IT?

HOW DOES IT WORK?

IN PRACTICE

ZERO TOE

POSITIVE (TOE-IN)

NEGATIVE (TOE-OUT)

Zero toe is not always ideal. First of all, even if you have zero toe (perfectly parallel front tires), once the driver takes his place on the kart and drives, in fact, the toe will tend to "close" (positive) due to the weight of the driver which affects the bending of the tubes, "C", etc. etc.